RB25DET Neo Compression Test Reference

[GTSBoy]

Hi All,

Sort of a humble brag masquerading as useful information. Whilst almost every other part of my car is currently falling apart, apparently the engine is in pretty good condition. My bro'-in-law just did a compression test on it (for reasons, explained below). The compression tester in question shall be regarded as being 100% trustworthy (for reasons, explained below).

Anyway, engine with well over 150000 km (I can't be bothered doing the sum required to work it out right now) tested at 175 psi on all cylinders. Nice.

We should consider that to be a reference compression test reading for a good Neo.

 

The story. Bro'-in-law comp tested an RB20 last week that had 3 at 115, 2 at 100 and one at 90, or something like that. Could not believe it because there was no signs of low compression in the way it behaved. It started quick and clean, drove perfectly, didn't smoke a lot, made decent power (for an RB20). So with some suspicion now placed on the comp tester, he compared it against 3 different digital manometers and it came up the same on all of them. So the gauge itself got a clean bill of health. Wanting to prove out the hose and fittings and such, he did the test on my (known to be pretty good) engine, which proved that the comp tester appears to be totally reliable. Thus, the RB20 is pretty buggered, and my engine is doing really well.

 

[admS15]

I'll add to your humblebrag, my own vanilla rb25 tested at 175psi across the board (warm) when i purchased the car 5-6 years ago on a accurate comp tester with a similar story. Engine was totally stock, stock boost. 60k kms on a Nismo cluster, so probably 200k kms.

 

5-6 years later of 310rwkw and over 30 track days, a couple of smashed gearboxes, a dead turbo and many many sets of tyres and brake pads. The engine recently comp tested at 160-165psi (cold) on the same gauge. I suspect that would increase a few psi at operating temp.

 

And they say rb's are weak. End humblebrag. Now that I've said that, I'll start researching rebuilds as the inevitable will likely happen very soon.

[GTSBoy]

15 minutes ago, admS15 said:

Now that I've said that, I'll start researching rebuilds as the inevitable will likely happen very soon.

I was holding onto the edge of the wooden desk the whole time I was typing!

[Ben C34]

In the interest of complete data can one of you guys crank up boost, hold on limiter etc and ping a ringland off and retest?

[GTSBoy]

15 hours ago, Ben C34 said:

In the interest of complete data can one of you guys crank up boost, hold on limiter etc and ping a ringland off and retest?

I let you hang for a while before replying, because you're not as funny as you think you are.

[KiwiRS4T]

I haven't done it on purpose but I have had an RB25 with broken ringlands and can confirm that it readily observable with a compression test,

[hypergear]

Yes I was get around 170psi on a healthy Neo motor as well. None Neo motor was sitting around 160psi.

[Unzipped Composites]

I had 182/3 across all 6 when I comp tested a few years ago. Done some k's since then, should get the comp tester out again and see how she's feeling these days!

[Dose Pipe Sutututu]

I don't even own a comp tester (well I did, but one of my mates borrowed it, moved houses and has lost it).

When in doubt, add boost.